The present invention is directed to systems and methods for monitoring patients during medical procedures and, more particularly, to systems and methods for determining when a patient is cognitively experiencing particular sensations.
Many types of medical procedures involve the use of anesthetics, analgesics, and other sedation or partial sedation methods. For example, general anesthetics are administered before some procedures to suppress pain throughout the patient's entire body. General anesthetics also render the subject unconscious and amnesiac during the procedure. These effects not only reduce stress on the subject, but also simplify the procedure for practitioners if the anesthetics are administered with immobilizing drugs (i.e., muscle blockers). That is, subconscious patient movements are prevented and therefore cannot interfere with actions of the practitioners and complicate the procedure.
Unfortunately, it can be difficult to precisely dose anesthetics or other drugs designed to sedate or render the patient amnesiac to achieve the desired effects because dose is determined by many factors including the subject's age, medical history, current medications, previous use of anesthetics, current condition (e.g., unstable or critical), and the like. Furthermore, some factors exacerbate the effect of others, and in some situations (e.g., if the subject is unstable) the subject's condition may completely obscure the effects of other factors. As such, for example, anesthesiology is largely based on heuristics and an anesthesiologist's experience.
The complexity of anesthesiology and other such undertakings sometimes results in insufficient dosing before medical procedures. In a small number of cases, this ultimately leads to unintended subject awareness (i.e., consciousness) or subconscious sensations of pain during the procedure. In the former case, the subject may not be able to communicate with medical practitioners if an immobilizing drug has also been administered. In these situations, the subject typically experiences panic and even lasting psychological problems after the procedure, such as post traumatic stress disorder.
Furthermore, the problems described above may also complicate procedures that involve regional anesthetics (i.e., anesthetics that only render part of the subject's body insensitive to pain). In these procedures, the subject remains conscious and, in some cases, may even need to move in a manner that assists in maneuvering medical equipment within the body. Nevertheless, the subject is typically heavily sedated in such procedures to reduce stress. As such, the subject may be incapable of communicating with practitioners regarding potential pain sensations and the ineffectiveness of anesthetics.
Complex methods of determining awareness of non-communicative subjects have been developed to address the problems described above. For example, functional MR images may show subject brain activity associated with awareness. However, conducting MR imaging during many types of medical procedures is impractical due to equipment unavailability, relatively large physical sizes, and relatively high operating costs among other reasons.
Therefore, it would be desirable to have an efficient, relatively inexpensive, and substantially objective method for recognizing subject consciousness and sensation of pain during medical procedures.